I am suddenly having difficulty starting my car. It will consistently turn over, but sounds as if it’s running down the battery - right away, I don’t sit for more than a few seconds with the ignition switch engaged. I turn the key to the off position and try again and it will has started up by the 3rd try every time so far. Once it starts, it runs great - no problems what so ever.
I replaced the battery about a month and a half ago so I suspected that perhaps I got a bad battery. I took the car by autozone to have them test the battery and alternator - both tested “good,” But I should note that this was actually the second time I took it to autozone this weekend and the battery tested good but low charge the first time (It was fully charged this time and I had just had trouble cranking. I thought I had just killed the battery because I was using a cell phone battery charge and thought it was just drawing too much).
I suspected the starter may be going bad, but I’m not sure because it will turn the engine over every time, it just doesn’t start. The girl at autozone suggested it may be the voltage regulator but I thought that that along with issues with the alternator itself would be noticeable if I ran the car with the lights, radio, etc on? I read that it could be the plugs or wires, but I would think in that case the battery wouldn’t sound as if it were run down right off the bat.
The next time you know the engine won’t start, turn thr ignition switch on for two seconds and then turn it off. Repeat this a half dozen times and then try starting the engine. If the engine starts everytime, there’s a problem with the fuel pump anti drain-back valve.
Tester
Follow Testers advice first and if it doesn’t work, then then I suspect that the battery is bad, especially if this started right after replacing the battery. The problem is that it might not show up even on a load test, especially if the person doing the test doesn’t understand the test completely.
The issue could be a marginal connection inside the battery. Here is how I would approach the problem. You need a volt meter or VOM to do this testing. Measure battery voltage with the key off. It should be around 12.6 volts.
Then keep measuring voltage as someone starts the car. While the starter is engaged, the voltage should drop to around 9 volts. If it goes lower than this, then either the starter is bad or the battery has a poor connection internally. If it is significantly higher and the starter is turning slower, you may simply need to clean your battery terminals.
If the voltage is lower, then the battery needs to be hooked up to a load tester. A load tester is pretty big and heavy, but it is portable. The test leads are the size of jumper cables and have large clamps on them. Typically the load tester measures the voltage as the battery discharges through a large resistor (aka dummy load). If the battery discharges quickly, it is bad, but that would be normal for an old battery. If your battery has a poor connection in it, it won’t discharge quickly, but will put out a steady voltage for the duration of the test. But that voltage will be lower than normal.
If the battery does test good, then you may have a bad starter.
After the car starts, the voltage across the battery should be between 13.8 and 15 volts. If it is below 13.4, the alternator is bad, above 15.1, the regulator is bad. The regulator may be built into the alternator so the alternator would have to be replaced anyway, or it may be part of the ECM. Many newer vehicles use the PCM to control the alternator now.
Your video appears to show a successful start, what would help is a video of an unsuccessful start.
BTW, a cell phone charger will not run down your battery.
Did you ever figure out what the problem was? I’m having the same issue. In my case, the car will turn over and start fine. More frequently now, when attempting to start on occasion it turns over and then winds down and stops right away like the battery is dying. But it is not. Battery has full voltage. It seems to happen more often on a warm start. Any help is greatly appreciated. An electrical diagram would also be of help. I can’t find the starter relay and that would be the first thing I want to try replacing.
I think the OP must have figure it out 5 years later. Some people just post a question and no longer show up on cartalk.
Curious if you were able to solve this…I know 2 years later 
In my case, it was a bad starter. Personally, I can’t imagine it being a relay as I would imagine that it would just be bad and do nothing rather than sounding as if the battery were draining.
I would try what Tester suggests, because it’s basically 0 effort. I didn’t have a multimeter at the time to do what Keith asked, but if you do, I’d try what he suggests.
You could try tapping on the starter with a stick, but it’s behind the intake, so it’s not exactly easy to do. This also makes this a more complicated DIY because the intake has to be removed and IIRC the radiator may need to come out to give you room to do it. If you are able to determine that it’s the starter and want to diy, I may still have the repair guide that I could scan and send you.